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jam jar jet from pvc cement can

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jam jar jet from pvc cement can

Unread postAuthor: meatballs » Tue Sep 04, 2007 11:17 am

i know you can make a sort of pulse jet type thing by putting methylated spirits in a jam or spaghetti sauce jar or something similar, and putting a whole in the lit ~10 mm wide and lighting it, and it cycles between flame shooting out, then sucking in more oxygen, at which point it shoots out more flame, there's an instructables on this at

http://www.instructables.com/id/EJ6JA1OD4CEXCFO3PQ

so i was wondering, could you make one of these using an empty pvc cement or primer can? that way there would be no glass to break.

and secondly, is methylated spirits the same as methanol? would ethanol work in one of these?

thanks, i appreciate any imput
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Unread postAuthor: spud yeti » Tue Sep 04, 2007 11:36 am

Yes you can, it even said you can build it out of metal on the site you linked.....the first post! :shock:
Dude, look next time!
Good luck anyways
(PS, dont forget the safety stuff even so :? )
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really good quote/phrase here
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Re: jam jar jet from pvc cement can

Unread postAuthor: jackssmirkingrevenge » Tue Sep 04, 2007 11:40 am

meatballs wrote:and secondly, is methylated spirits the same as methanol? would ethanol work in one of these?


That would be ethanol that has been rendered unsuitable for human consumption ;)

I wouldn't call the result a "pulse jet" though.
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Unread postAuthor: goathunter » Tue Sep 04, 2007 12:38 pm

Boy that is one special instructable :roll:

All the guy did was make a very junky alcohol burner.

But jack is right.Methylated spirits is ethanol with a enough methanol and dye in it so that you won't drink it.
Methanol will turn to formaldehyde once your body processes it.Good if you want to go blind then save on embalming costs.But otherwise not a good thing to have around.

You can use ethanol or methanol in the place of Methylated spirits.I use all three in my camping stoves.Works fine.And maybe I should start calling them jet engines instead of stoves :D
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Unread postAuthor: paaiyan » Tue Sep 04, 2007 1:06 pm

Well first of all, I don't know that that would have enough power to actually push anything, and two, that thing made some really awkward noises.
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Unread postAuthor: jimmy101 » Tue Sep 04, 2007 1:47 pm

The instructable isn't all that bad.

It really is a pulse jet and not an alcohol burner. An alcohol burner would not cause the glass jar to overheat and break. Alcohol burners are designed to not suck the flame front back into the container, they don't get hot, and they don't fracture even if they are usually made with glass containers.

Alcohol burners don't make any noise. The fact that this does make noise mean it is generating pressure pulses.

Granted, it sucks as a propulsion source, but what do you expect from a jar with a hole in the lid?

Critiquing the instructable as "not a real jet engine" is kind of like a rifle enthusiast critiquing spud guns as "not real guns" because they are made out of plastic and fire potatoes.
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Unread postAuthor: goathunter » Tue Sep 04, 2007 2:31 pm

Now here comes a whole different argument.

"An alcohol burner would not cause the glass jar to overheat and break. Alcohol burners are designed to not suck the flame front back into the container, they don't get hot, and they don't fracture even if they are usually made with glass containers.

Alcohol burners don't make any noise. The fact that this does make noise mean it is generating pressure pulses."-jimmy


How many times have you made an alcohol burner?Burners are quite capable of busting glass and annealing metal for that matter.Soda pop stoves only last for a week or so before they get too annealed to be useful.And the reason they don't suck the flame back in is because they have proper air inlets so the flame doesn't have to die down before a new batch of oxygen gets in and the mixture combusts once again.If you took out the air inlet in the middle the burner would function as the Jam Jar Jet did.
Burners make lots of noise.If the jets are made right you can get sounds varying from a whistle to a full blown roar.
[/quote]
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Last edited by goathunter on Tue Sep 04, 2007 3:04 pm, edited 1 time in total.
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Unread postAuthor: meatballs » Tue Sep 04, 2007 2:47 pm

great, thanks for the input. i guess in that case i was using methylated spirits the whole time, cause my ethanol is ~5% methanol.
and i just had another idea. maybe i could use a tomato soup can (or a broth can or a can of anything else runny) if i just opened it by drilling a whole in it. does anyone know what would work better, methylated spirits or methanol?
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Unread postAuthor: jimmy101 » Tue Sep 04, 2007 4:37 pm

There are a lot of different types of alcohol burners. I was referring to the most common, basically a kerosene lamp which has a wick.
Image

No noise. Can be operated indefinitely without any problems relating to heating of the fuel reservoir.

Burners are quite capable of busting glass and annealing metal for that matter.

The point is NOT what you can DO with the burner (melting glass, annealing metal) the point is what happens to the burner itself. Same with a propane torch, you can melt soft glass, anneal metal etc. but unless you leave the torch lit for a long time the cylinder does not heat up and fail.

I've never seen an alcohol burner make much noise. Any burner that uses a forced fuel supply will make noise. Compressed gas, or heated volatile liquid from a closed reservoir, will make noise. An unpressurized system will not.
No noise. Can be operated indefinetly without any problems relating to heating of the fuel resevoir.

The "pulse jet" being discussed is an open system that behaves like a pressurized system.
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Unread postAuthor: goathunter » Tue Sep 04, 2007 5:21 pm

I was talking about one of these.They pressurize and act similar to the "Pulse Jet".
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Unread postAuthor: jimmy101 » Tue Sep 04, 2007 5:46 pm

Nope, that doesn't work similar to a "pulse jet". It works the same as a propane torch or Bunsen burner. Completely different mechanisms. Though the burner you are referring to does use some of the heat generated to pressurize the fuel.

The one you are referring to and burns continuously.

The other uses unpressurized fuel and pulses (hence the name). The pressure in the fuel reservoir oscillates between > than ambient and < than ambient
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Unread postAuthor: meatballs » Tue Sep 04, 2007 7:38 pm

goathunter where did you get that picture? thats not what i posted about but it looks really cool and i may have to try making one.
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Unread postAuthor: jackssmirkingrevenge » Tue Sep 04, 2007 11:09 pm

If you want something jet-like that will actually move (and you can mount it on a toy boat as opposed to a sardine can), have a look at this.
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Unread postAuthor: benstern » Wed Sep 05, 2007 12:52 am

You can make hybrid rocket from some tar or other long hydrocarbon (paraffin wax I heard is good) and oxygen (nitrous oxide is way better) from the hardware store.
http://video.google.com/videoplay?docid ... 0425073135
http://video.google.com/videoplay?docid ... 0425073135
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Last edited by benstern on Wed Sep 05, 2007 12:57 am, edited 1 time in total.
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Unread postAuthor: Insomniac » Wed Sep 05, 2007 12:55 am

The jam jar jet is a pulsejet that is more useful for heating than propultion. While it may give some thrust, it will be very weak and will need modification to run on its side. The proper name for these is a Reynst combustor. And any thrust they generate will be from the gas going out, not in. If sucking air generated any appreciable thrust, harrier jump jets wouldn't work because the intakes still face foward while the outlets pivot, which would cause the jet to go flying foward while trying to hover.
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